A suspension fork for cycles includes adjustment means operable by the rider externally of the fork for selectively controlling the extent of relative axial travel of the telescopic leg sections of the fork.
The adaptation of suspension elements to the front forks of bicycles has increased the functionality of the bicycle and the enjoyment thereof by the user by insulating the rider from the bumps or obstacles in the road or trail. Early suspension forks had only 50 mm of travel, which at the time seemed to be a great improvement. As riders adapted to the increased off-road abilities of bicycle due to the suspension fitted to the bicycle, they soon sought even more suspension travel to be able to attack more difficult terrain and at higher speeds.
As suspension travel increased, it became apparent that improved comfort and control riding rough or downhill terrain could be achieved with ever longer travel forks. However, it also became apparent that with this increased travel, there was a compromise in the ideal bicycle geometry or riding position for riding on level or uphill terrain. This left the rider with a need to choose between a suspension optimized with longer travel for rugged downhill terrain or somewhat shorter travel for efficiency on smoother and uphill terrain.
The first attempt to build a suspension fork that addressed this multi-travel need was taught by the Stewart, et al., U.S. Pat. No. 5,470,090. This invention allowed the user to assemble the same fork in two different configurations, one being a short travel version and one being a longer travel configuration. This allowed the rider to better optimize his fork to riding different terrain without having to buy two different forks or switch forks on the frame. However, this design did require considerable disassembly and re-assembly of the suspension fork to effect the change from long travel to short travel, which was not convenient or often utilized by the end user.
The next improvement in forks with multi-travel capabilities was the Rock Shox PSYLO fork. This improvement allowed the user to adjust the fork travel by turning a screw located inside the stanchion (inner leg). This used a screw type ramp mechanism to shorten or lengthen the fork travel within a range to better suit the particular terrain to be ridden. Although this method did not require considerable disassembly of the fork, which was a significant improvement, it did require the user to stop riding the bicycle, obtain tools and remove some elements of the fork to gain access to the adjusting mechanism and then replace them before continuing on.
The present invention was developed to provide a new improved suspension fork for cycles, such as bicycles and motorcycles, wherein the rider could utilize the clear advantages of a fork, the travel of which could be adjusted to best suit the particular terrain the rider encountered during the course of the ride. During many typical rides, many types of terrain and riding conditions are encountered and the potential existed for the need to change the travel characteristics of the fork several times even during the same ride. The key to product success was to allow the end user to adjust travel xe2x80x9con the flyxe2x80x9d with on-off switch convenience. This needed to be accomplished by the rider out on the trail with no tools and no fork disassembly; as simple as a flip of a lever.
Accordingly, a primary object of the present invention is to provide a suspension fork for cycles including adjustment means operable by the cyclist externally of the fork for adjusting the relative length of travel between the telescopic sections of at least one leg of the suspension fork. Preferably an adjustment knob or lever is arranged at either the bottom or the top of the fork leg at a location readily accessible to the cyclist, whereby the travel adjustment is easily and positively accomplished without the need of any tools and/or any disassembly of the fork.
According to a more specific object of the invention, the compression rod that is contained within the telescopic sections of the leg and which cooperates with the compression spring to bias the sections apart toward an expanded condition is hollow and includes alternately retractable and extensible stop means that are operable externally of the fork leg. These stop means are arranged intermediate the first and second travel limiting means of the fork, whereby when the stop means are in the extended condition, the relative length of travel of the telescopic leg sections is shortened.
According to another object of the invention, the stop means includes at least one stop dog that is displaceable from a retracted position within the hollow compression rod to an extended position in which the stop dog extends partially outwardly of the compression rod via a slot contained in the wall thereof. Various types of operating means may be used for displacing the stop dog to its extended position, including wedge means, cam means, and rotary operating means.
According to the preferred embodiment of the invention, a pair of stop dogs extend outwardly via opposed slots contained in the compression rod. The stop dogs include longitudinally extending pivot shafts that extend within eccentrically arranged bores contained in one end of an inner cylindrical operating member that is rotatably mounted coaxially within the compression rod. According to an important feature of the invention, the operating lever or knob that is externally arranged on the upper or lower end of the fork is coupled to the cylindrical operating member via a torsion overload spring, thereby to achieve positive extension or retraction of the stop dogs. Preferably, the stop dogs are provided with angularly arranged surfaces that prevent the stop dogs from being caught on the end of the rebound spring or on the rebound spring capture means.
According to a further object of the invention, a set of sliding stop dogs is used to control the position of the stanchions relative to the outer assembly. The true advantage of this feature is to allow the user to have the benefit of a short travel fork for climbing and a long travel fork for descent all in one fork, accessed by at the mere flip of a lever. The addition of a torsion spring, between the lever and sliding dogs, allows for the travel to be set at any point in the stroke of the fork. Once set, the travel will be limited during the stroke or at the next stroke (depending upon the position selected). The particular execution of the travel adjustment means utilizes a switching adjustment lever at the bottom or the top of the leg of the suspension fork. By placing the adjustment knob at the top of the fork, and ever greater level of rider convenience is provided for switching travel length to meet varied terrain and riding conditions without the need for stopping or dismounting the bicycle.